A vaccine to prevent breast cancer has shown overwhelmingly favorable results in animals, according to a study by researchers at Cleveland Clinic's Lerner Research Institute.

They found that a single vaccination with the antigen a-lactalbumin prevents breast cancer tumors from forming in mice, while inhibiting the growth of existing tumors.

Human trials could begin within a year.

If successful, it would be the first vaccine to prevent breast cancer, reports CBS Cleveland affiliate WOIO.

"We believe this vaccine will someday be used to prevent breast cancer in adult women in the same way that vaccines prevent polio and measles in children," Vincent Tuohy, Ph.D., the study's principal investigator and an immunologist at the Lerner Institute, told WOIO..

"If it works in humans the way it works in mice, this will be monumental. We could eliminate breast cancer," he added.

While the researchers are optimistic, they warn it's a big leap from results in animals to similar results in humans.

In the study, genetically cancer-prone mice were vaccinated -- half with a vaccine containing the antigen and half with a vaccine that did not contain the antigen. None of the mice vaccinated with the antigen developed breast cancer, while all the other mice did.

The Food and Drug Administration has approved two cancer-prevention vaccines, one against cervical cancer and one against liver cancer. But those vaccines target viruses -- the human papillomavirus (HPV) and the Hepatitis B virus (HBV) -- not cancer formation itself.

Cancer presents a quandary that viruses don't in terms of developing vaccines, experts point out. While viruses are recognized as foreign invaders by the immune system, cancer isn't. Cancer is an over-development of the body's own cells. Trying to vaccinate against such cell over-growth would effectively be vaccinating against the recipient's own body, destroying healthy tissue.

The key, Tuohy said, is to find a target within the tumor that isn't typically found in a healthy person. In the case of breast cancer, he and his team targeted a-lactalbumin, a protein found in the majority of breast cancers, but not in healthy women, except during lactation. Therefore, the vaccine can rev up a woman's immune system to target a-lactalbumin, stopping tumor formation without damaging healthy breast tissue.

The strategy could be to vaccinate women over 40, when breast cancer risk begins to increase and pregnancy becomes less likely. (If a woman would become pregnant after being vaccinated, she would experience breast soreness and would likely have to choose not to breast feed)

For younger women with a heightened risk of breast cancer, the vaccine may be an option to consider
instead of prophylactic radical mastectomy, researcher say.

"Most attempts at cancer vaccines have targeted viruses, or cancers that have already developed," said Joseph Crowe, M.D., Director of the Breast Center at Cleveland Clinic. "Dr. Tuohy is not a breast cancer researcher, he's an immunologist, so his approach is completely different - attacking the tumor before it can develop. It's a simple concept, yet one that has not been explored until now."

Tuohy believes the findings of this study go beyond breast cancer, providing insight into the development of vaccines to prevent other types of cancer.

The results show that the antigen used in a cancer vaccine must meet several criteria: It must be over-expressed in the majority of targeted tumors; and it must not be found in normal tissue, except under specific, avoidable conditions (such as lactation).